Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

AS Level > Chem Unit 2 (Alkenes) > Flashcards

Chem Unit 2 (Alkenes) Flashcards

1
Q

Alkenes (homologus series so.. [2 things]

A
  • same functional group (CnH2n)

- same structural formula (C=C)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

As you increase chain length…

A

number of van der waals increases so melting and boiling point increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Why are alkenes more reactive?

A

pi bond has delocalised electrons that are hel less tightly and attract positively-charged atoms/groups

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Double bond is made up of ?

A

pi bond and stigma bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Why are alkenes double-bonded?

A 
unsaturated- can accept hydrogens (still need to make 4 single, covalent bonds, 
sigma binds (bond 3 atoms covalnetly)
still need pi (double bond 1 pi, 1 stigma) to make 4 bonds.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Why di akenes take more energy to break?

A

pi bond and sigma bond brings carbon atoms closer together- held more tightky

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Why can’t there be positional isomers of alkenes?

A

C=C bond is rigid/planar structure

atoms/grouos attached to it are fixed- so there can’t be positional isomers- Only CHAIN GEOMETRIC ISOMERS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Z isomer.. methyl groups are on..

A

same side of carbon atom

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

E isomers..methyl groups are on..

A

opposite side of carbon atom

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is electrophilic addition?

A

Electrophiles (positevely charged molecules/atoms ) accept a pair of electrons from the area of high electron density in the double bond (pi bond)
breaks the double bond > turns it intoa single bond (alkane)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Electrophilic addition: why is Bromine a dipol-dipole in the presence of..?

A

ethene- the double bond of the ethene induces a temporary dipole-dipole

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

When a hydorgen halide reacts with a unsymmetrical alkene it can make..?

A

diferent products becuase it depends on which end of the double bond the hakide reacts with e.g. 1-bromo-propane or 2-bromo-propane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

The major prodcuct (whats mostrly formed) is going to be the secondary carbocation and the minor product the primary carbocation because?

A

Secondary carbocation is more stable than primary one
Order: primary>secondary>tertiary
because for primary the c+ is bonded to one other carbon atom (could be a methyl group, halogen atom) , fior secondary 2, tertiary -3
These carbon atoms donate electrons so minimise the positie charge on the carbocation, making it more stable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Add bromine water to alkenes>

alkanes>

A 
alkenes = colourless (unsaturated)
alkanes = yellow (saturated)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

carbon neutral?

A

no net carbon emissions into the atmosphere

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Making an alkene into an alcohol with sulfuric acid?

A

conc. H2S04 . alkene
warm it with dilut H2S04 and water > alcohol = H20
sulfuric acid is a catalyst- unchanged but sppeds up rate of reaction so is recycled.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Why is ti hydration?

A

overall addition of water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Hydrogenation of vegable oils condtions?

A
  • Hydrogen

- heat to 60 degrees

19
Q

Conditions for producing ehtanol by hydration (steam)

A

phosphoric acid catalyst- sulfuric acid too corrosive too use on a large scale
fairly low temp = 300 degrees
high pressure = 600-7000 kpa
high concentration of steam
5% intial yield but 95% with recyling of unreacted ehtene and steam

20
Q

yield for ethanol isn’t 100% by hydration as?

A

methanol and polyethene are made as side reactions

21
Q

Advantages of ethanol production by steam?

A
  • quick
  • continued recycling of ethene and steam
  • no pollution
  • high yield
22
Q

Disadvantages if ethanol production by steam?

A
  • crude oil (non-renewable)
  • high pressure (costs)
  • high temperature (costs)
23
Q

polymers are

A

large molecule made up of thousands of monomers

24
Q

momomer is..

A

small molecules that jon together to maje a polymer

25
Q

addition polymerisation

A

momomers are added together to make polymers

26
Q

Why is polyethene fairly unreactive?

A

100% yield > polyethene no double bond so can’t do much

can do combustion

27
Q

If polyethene makes LDPE?

A

softens under high temepratures
branched- can’t pack closely together
used for bags, plastic botttles

28
Q

If polyethene makes HDPE?

A

titanium chloride/triethyl aluminium catalyst
60 degrees/atmsopheric pressure
straight-chain alkanes > buckets/crates

29
Q

poly(propebe) if CH3 ad H groups are arranged facing in same direction…

A

isotactic (used for car bumpers)

30
Q

poly(propebe) if CH3 ad H groups are arranged randomly…

A

actactic (versatile plastic properties mid-way between HDPE and LDPE

31
Q

Bipol

A

produced by microbes

eaten by other microbes> decompose it releasing C02 (limited-expensive)

32
Q

Digesting material

A

polymer material is digested by microbes (e.g bacteria/fungi)
C=0 (carbonyl group) means tis easier
plymers containing chlorine, benzene or methyl groups are resitant to the microbes.

33
Q

polymer material that is broken down in the presence of light is..

A

photodegradable

34
Q

Co polymers

A

ethene + CO > Copolymer
C=0 (carbonyl group) absorbs energy from light
increased light energy breaks bonds in copolymers e.g. ETFE

35
Q

Photodegrading plastics are ideal for plastics that can’t be easily?

A

recovered (e.g. fishing nets)

36
Q

If plastics are dumped in landfill they lack…?

A

light, oxygen, microbes so take a long time to bioddegrade

37
Q

Main problems with recycling plastics?

A
  • High levels of contamination

- Many types so difficult to sort

38
Q

mechanical recycling means:

A

plastic has to be sorted and cleaned first

shredded > melted down into pellets > remoulded into new objects

39
Q

Chemical recylcling is …?

A

don’t aghve to be sorted and cleaned
heat and a catalyst ( like thermal cracking) to break long chains into shorter chains and small molecules like ethane and ethene (useful)

40
Q

If plastics are sorted/cleaned enough it is possible to process them back into..?

A

their monomers

41
Q

Thermal recycling?

A

Equal masses of crude oil and plastic have similair amounts of stored enrgy.
When plastic is burned > energy used to generate steam/electricity
problem with plastics containing chlorine, it releases doxins into atmosphere

42
Q

3 main way to produce ethanol:

A
  1. Hydration by steam
  2. Using yeast to ferment plant sugars
  3. using bacteria to produce it from biomass waste
43
Q

Conditions for thermal cracking?

A
  • High temperature
  • nickel catalyst
  • High pressure

AS Level (74 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions